Rabiul Hasan
Department of Environmental Science, Bangladesh Agricultural University Mymensingh 2202, Bangladesh
Rehana Khatun
Department of Environmental Science, Bangladesh Agricultural University Mymensingh 2202, Bangladesh
Md. Abdul Baten
Department of Environmental Science, Bangladesh Agricultural University Mymensingh 2202, Bangladesh
Two field experiments were conducted at Bangladesh Agricultural University campus and Gonsar Mor, Mashkanda, Mymensingh during January to May 2018 to evaluate the nutrients and heavy metal contents in soil and crop. Freshwater and wastewater irrigation and four varieties of rice: V1 (BINA dhan11), V2 (BRRI dhan28), V3 (BRRI dhan29) and V4 (BRRI dhan58) were used with three replications. Analyses of wastewater for pH, EC, DO and heavy metals (Pb, Ni Cd and Cr), soil (before land preparation and after harvest) for pH, EC, OM, N, P, K and heavy metals (Pb, Ni, Cd, Cr), straw and grain for N, P, K and heavy metals were done using standard methods. The pH, EC, Pb, Ni, Cd and Cr content of wastewater was 7.4, 0.612 mS cm-1, 4.3 ppm, 0.09 ppm, 0.40 ppm and 1.80 ppm, respectively. The values of pH, EC, Pb and Ni were within the permissible limit whereas Cd and Cr content in wastewater exceeded the permissible limit for irrigation. OM, N, P and K contents were higher in wastewater irrigated soil and average Cd (0.014 ppm) and Cr (44.81 ppm) content of soil under wastewater irrigation was within the permissible limit. Nutrients and heavy metals (Cd: 0.001 to 0.006 ppm; Cr: 0.49 to 0.59 ppm) contents of straw and grain were also higher under wastewater irrigation. Bioaccumulation and translocation factors for Cd ranged from 0.103 to 0.431 and 0.097 to 0.865 and for Cr ranged from 0.011 to 0.013 and 0.010 to 0.012, respectively. Significant variations were found among four varieties regarding nutrient contents of straw as well as bioaccumulation and translocation of Cd in grain. Bioaccumulation factor was <1, indicating absorption only, not accumulation of Cd and Cr in straw or grain, and municipal wastewater can safely be used as an alternate water source for irrigation. Collection and analysis of plant sample Fully mature rice was harvested on 15 May 2018. Above ground plant parts (straw and rice) were used for the analysis of total N, available P and exchangeable K, Cd and Cr. Assessment of bioaccumulation and translocation of heavy metals Bio-accumulation factor (BAF) The BAF of heavy metals in the plant samples was calculated as: BAF = Cplant/ Csoil Where, Cplant is the concentration of the element in the plant, and Csoil is the concentration of same element in the soil on dry weight basis. Translocation factor Translocation of heavy metals from the soil to the edible parts of the crop was determined by the accumulation factor (AF) (Li et al., 2012). All the experimental data were statistically analyzed using MS Excel 2013 and MiniTAB 17.0 data processing software.
Municipal wastewater irrigation, Nutrient, Heavy metals, Bioaccumulation, Translocation
Mymensingh, Bangladesh
Risk Management in Agriculture
Contamination of soil, Contamination
Site selection: The wastewater of Mymensingh Municipal area is released at Noyapara outlet and passing through channel from Mashkanda to Chorar Beel area. From January to March in every year, the farmers of these peri-urban areas have no other alternative to use municipal wastewater as irrigation for rice cultivation due to shortage of water. Gonsar Mor, Mashkanda, the nearest wastewater releasing point was therefore selected for this study. However, in Gonsar Mor area, there is no availability of fresh water for irrigation purpose due to absence of deep tube well. Therefore, Field Laboratory of Department of Environmental Science, BAU, Mymensingh was selected for setting an experiment under fresh water irrigation to compare the results with that of wastewater irrigation. Environmental Science Field Laboratory is located at 24.75°N latitude and 90.50°E longitude and the rice field of Gonsar Mor, Mashkanda is located at 24.45°N latitude and 90.22°E longitude. The both sites belong to the Sonatola soil series of non-calcareous dark grey flood plain soil under the Old Brahmaputra Alluvial Tract and are characterized by moderately high temperature and heavy rainfall during the Kharif season (April-September) and scanty rainfall with moderately low temperature during Rabi season (October- March). Experimental design and layout The study was carried out during the period from 16 January to 15 May 2018. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. Irrigation water was used as main treatment in this study. Treatments were: T1: Fresh water irrigation and T2: Municipal wastewater irrigation. Varietal effects under irrigation were also investigated in this study. Varieties were: BINA dhan11 (V1); BRRI dhan28 (V2); BRRI dhan29 (V3) and BRRI dhan58 (V4). The total numbers of unit plots were 24. The area of each plots was 20 square meter (5m × 4 m). The treatment combinations were randomly distributed to unit plots. Crop establishment The land was first opened on 16 January 2018. In municipal wastewater irrigated area, farmers do not use the recommended doses of fertilizer due to high nutrient content of soil. Only 300 g MOP was applied per plot during final land preparation and after 60 days of transplanting, 200g urea was applied in each plot. In fresh water irrigated land, fertilizer was applied following the recommended doses. Seedlings were transplanted in well prepared land maintaining three seedlings per hill with 15 cm × 20 cm row and hill spacing on 21 January 2018. Necessary intercultural operations were done for maintaining the normal growth and development of the crop. Collection and analysis of wastewater Wastewater was collected from the drain of Gonsar Mor rice field for the analysis of pH, EC, DO and heavy metals (Pb, Ni, Cd and Cr). The pH, DO and EC were measured by pH meter (model: pHep, HANNA Instruments), DO meter (model:YK-22DO) and EC meter (model:3251, COND/TEMP/METER), respectively at the Laboratory of Department of Environmental Science, BAU, Mymensingh. Heavy metals (Pb, Ni, Cd, Cr) were analyzed at Bangladesh Agricultural Research Institute (BARI), Gazipur by Atomic Absorption Spectrophotometer (AAS) (Varian spectra AA55B, Australia). Collection and analysis of soil samples The soil sample of fresh water irrigated land and municipal wastewater irrigated land was collected from 0-15 cm depth before final land preparation and after harvest for the analysis of total nitrogen (N), available phosphorus (P), exchangeable potassium (K) and heavy metals (Pb, Ni, Cd and Cr) content. The N content was estimated by micro-Kjeldahl method, total P was extracted from the soil following the method of Olsen et al. (1954), total K was determined using flame photometer (Black, 1965) at the Laboratory of Department of Soil Science, BAU, Mymensingh. Pb, Ni, Cd and Cr were analyzed at BARI, Gazipur.
J Bangladesh Agril Univ 18(1): 47–54, 2020
Journal